Strapping tool

ABSTRACT

A pneumatically powered combination strapping tool for applying a loop of strap around an object includes means for tensioning the strap, joint forming mechanism for securing together the overlapping ends of the tensioned strap, strap guide members coupled to and movable with the joint forming mechanism between a retracted position away from the strap loop and a strap guiding position spanning the overlapped portions of the strap for limiting lateral movement thereof, drive means for effecting movement of the joint forming mechanism and strap guide members, and control means operative in response to actuation of a single control lever for operating the tool through an entire strap applying operation. The control apparatus is operative for moving the strap guide members to the strap guiding position thereof simultaneously with the initiation of the tensioning operation to insure maintenance of the end portions of the strap loop in overlapping relationship during tensioning to facilitate the formation of the joint, the strap guide members automatically being returned to the retracted position at the completion of the joint forming operation.

United States Patent Simmons [451 Feb. 4, 1975 STRAPPING TOOL [75] Inventor: James R. Simmons, Frankfort, Ill.

[73] Assignee: lnterlake, Inc., Chicago, Ill.

[22] Filed: Nov. 23, 1973 211 Appl. No.: 418,231

Primary Examiner-Lowell A. Larson Attorney, Agent, or F irm- Prangley, Dithmar, Vogel. Sandler & Stotland [57] ABSTRACT A pneumatically powered combination strapping tool for applying a loop of strap around an object includes means for tensioning the strap, joint forming mechanism for securing together the overlapping ends of the tensioned strap, strap guide members coupled to and movable with the joint forming mechanism between a retracted position away from the strap loop and a strap guiding position spanning the overlapped portions of the strap for limiting lateral movement thereof, drive means for effecting movement of the joint forming mechanism and strap guide members, and control means operative in response to actuation of a single control lever for operating the tool through an entire strap applying operation. The control apparatus is operative for moving the strap guide members to the strap guiding position thereof simultaneously with the initiation of the tensioning operation to insure maintenance of the end portions of the strap loop in overlapping relationship during tensioning to facilitate the formation of the joint, the strap guide members automatically being returned to the retracted position at the completion of the joint forming operation.

15 Claims, 11 Drawing Figures PATENTED 4%975 SHEET 10F 6 PATENTED FEB 9 5 SHEET 2 0F 6 PATENTED 41975 SHEET 30F 6 1 STRAPPING TOOL BACKGROUND OF THE INVENTION The present invention relates to improvements in strapping tools of the type used for applying a seal to overlapping ends of a strap loop, and more particularly is concerned with a pneumatic type power strapping tool that is of simplified construction and is capable of fully automatic operation through an entire tensioning and sealing cycle. Specifically. the present invention is an improvement of the strapping tool disclosed in US. Pat. No. 3,396,760, issued to P. Kirsinas, et al., on Aug. 13, 1968, and assigned to the assignee of the present invention.

The strapping tool disclosed in the Kirsinas, et al., patent and similar prior art devices are semi-automatic in operation in that they employ a plurality of control instrumentalities, each of which requires a manual operation, in order to complete a single tensioning and joint forming cycle of the tool. Thus. for example, operation of the Kirsinas, et al., tool requires manual operation of a first lever to set the tensioning means in operation and then, when the tensioning motor stalls out, a second lever must be manually operated to actuate the seal forming operation.

Furthermore, a disadvantage of this type of prior art tool has been its lack of adequate guiding of the overlapping strap ends during the sealing operation. Thus, if the ends of the strap loop had not been loaded properly in the tool, it was possible that during tensioning operation the overlapping portions of the strap would be pulled out of overlapping alignment with each other. This would seriously impair the formation of the seal joint between these overlapping strap ends, because the seals are only slightly wider than the strap band and are dimensioned to fit snuggly thereabout. Thus, applica tion of the seal about the misaligned strap ends would result in bending or folding of the strap ends or shearing thereof. thereby seriously impairing the sealed joint therebetween.

US. Pat. No. 3,506,041. issued to B. R. Angarola on Apr. 14, I970, discloses a pneumatic strapping tool similar to that disclosed in the Kirsinas, et. al., patent, but which permits fully automatic operation of the tool through a complete tensioning and sealing cycle in response to operation of a single control instrumentality. However, it has been found that the tension-sensing mechanism in the Angarola device does not accurately detect the predetermined tension at which sealing is desired to take place. Furthermore, the Angarola device lacks any adequate guidance of the strap during the tensioning operation, whereby it is susceptible to the misalignment and improper scaling in the same manner as is the apparatus of the Kirsinas, et al., patent.

SUMMARY OF THE INVENTION The present invention provides a pneumatically operated strapping tool which provides for fully automatic operation through an entire tensioning and sealing cycle in response to a single control lever, while at the same time providing strap guiding means for guiding the overlapping portions of the strap loop during tensioning operation.

It is an important object of the present invention to provide a strapping tool for applying a length of strap around an object in a loop with overlapping end portions, the strapping tool comprising tensioning means for tensioning the loop of strap about the object, joint forming mechanism for forming a joint between the overlapped portions of the tensioned strap to secure the strap about the object, strap guide means movable between a retracted position away from the strap loop and a strap guiding position closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, and means for moving the strap guide means to the strap guiding position thereof at the initiation of the tensioning means and for moving the strap guide means back to the retracted position thereof after formation of the joint in the tensioned strap, whereby the strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate formation of the joint.

in connection with the foregoing object, it is another object of this invention to provide a strapping tool of the type set forth which includes drive means coupled to the strap guide means for effecting movement thereof between the retracted and the strap guiding positions thereof, and control apparatus coupled to the drive means and actuating same to move said strap guide means to the strap guiding position thereof at the initiation of operation of the tensioning means and for moving the strap guide means back to the retracted position thereof after formation of the joint in the tensioned strap, thereby providing an automatic strapping operation,

In connection with the foregoing object, it is another object of this invention to provide an automatic strapping tool of the type set forth, wherein the drive means includes bias means resiliently urging the strap guide means toward the strap guiding position thereof, and fluid-actuated means having an energized condition for normally holding the strap guide means in the retracted position thereof against the urging of the bias means and a deenergized condition for permitting the strap guide means to move to the strap guiding position thereof under the urging of the bias means.

Still another object of this invention is to provide an automatic strapping tool of the type set forth. wherein the strap guide means is coupled to the joint forming mechanism and movable therewith among retracted. strap guiding and sealing configurations.

Yet another object of this invention is to provide an automatic strapping tool of the type set forth, wherein the control apparatus includes a plurality of fluid valves interconnected to provide completely automatic opera tion of the tool through an entire tensioning and joint forming cycle.

Further features of the invention pertain to the particular arrangement of the parts of the automatic strapping tool whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation. together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS H6. 1 is a side elevational view of a strapping tool constructed in accordance with and embodying the features of the present invention, with the tensioning motor shown disposed in its working position;

H6. 2 is a fragmentary top plan view of the strapping tool illustrated in FIG. I, with the drive cylinder shown in horizontal section to illustrate the internal construction thereof;

FIG. 3 is a cross-sectional view of the tensioning motor and tension sensing valve taken along the line 3-3 in FIG. I.

FIG. 4 is a cross-sectional view of the tension sensing valve taken along the line 4-4 in FIG. 3;

FIG. 5 is a front elevational view of the tensioning tool illustrated in FIG. I. with portions of the air hoses broken away;

FIG. 6 is a fragmentary view in horizontal section taken along the line 66 in FIG. I and illustrating the joint forming and strap guiding mechanism of the present invention;

FIG. 7 is a rear elevational view of the strapping tool illustrated in FIG. 1;

FIG. 8 is a fragmentary view in vertical section taken along the line 88 in FIG. 6 and illustrating one of the strap guide members of the present invention;

FIG. 9 is a top plan view of the valve body casting of the present invention;

FIG. 10 is a fragmentary view in vertical section taken along the line l0l0 in FIG. 9, illustrating the internal construction of the valve body casting and the sealing valve actuating assembly; and

FIG. II is a schematic pneumatic circuit diagram showing the pneumatic control mechanism by which the tool of the present invention is operated.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIGS. I, 2, S and 7 thereof, a preferred embodiment of an automatic power strapping tool 20, constructed in accordance with and embodying the features of the present invention. is shown for purposes of illustrative disclosure as including the following principal structural elements generally familiar to those skilled in the strapping tool art: a base 21, a tensioning assembly 30 including an air motor 40, a sealer drive assembly 80 driven by a main drive cylinder 70. and a valve body casting I for controlling the operation of the tensioning and sealing apparatus in applying a strap S about an object. Each ofthese main structural elements is essentially similar to corresponding structural elements in the strapping tool disclosed in the aforementioned U.S. Pat. No. 3.396.760. reference to which patent may be had for a detailed explanation of the structure and operation of these elements. Only so much of these main elements will be here described in detail as is necessary for a clear understanding of the present invention.

Fixedly secured to the base 21 is an upstanding front side plate 22 and a rear side plate 23 spaced from and parallel to the front side plate 22 and cooperating therewith to define a chamber to accommodate the seal forming mechanisms. The base 2] serves as one of the principal structural elements relating the fixed parts of the tool and it includes a horizontally enlarged contact foot portion 24 to be engaged against the package or article that is to be tied, and an integral upstanding side wall 25 provided with a set of externally projecting apertured lugs (not shown) to receive a pivot pin 27. Secured to the base 2] at the rear end of the strapping tool 20 is a bottom handle 28 to facilitate handling and movement of the tool 20.

As best seen in FIGS. I and 5, the tensioning assembly 30 includes a tensioning drive housing 31 provided with a gear box portion and a main sleeve portion 34 which is provided with internal needle hearings (not shown) to receive a rotary dog shaft 36 which drivingly engages a rotary dog 35. A cover 37 normally closes one end of the tensioning drive housing 3| and serves to mount a ball bearing assembly (not shown) for receiving one end of the rotary dog shaft 36. The rotary dog shaft 36 is splined to receive a spiroid gear adapted for meshing engagement with a spiroid pinion on the shaft of the air motor 40. as is more fully explained in the aforementioned US. Pat. No. 3.396.760. The other end of the rotary dog shaft 36 is reduced and is carried in a bearing element 29 which is swingably mounted on the end ofthe pivot pin 27. Integral with the bearing element 29 and extending upwardly therefrom is a bearing support 32 for a purpose which will be described more fully below.

The tensioning air motor 40 is a rotary type pneumatic motor driven by compressed air supplied to the air motor 40 through an air hose 42 and an inlet fitting 4| from an external air source 43 (see FIG. II). The details of construction of the air motor are well known and are therefore omitted from this disclosure. The housing for the air motor 40 is assembled to a flange re gion of the tensioning drive housing 31, and the motor 40 has an output shaft (not shown) in driving engagement with the rotary dog shaft 36. The tensioning drive housing 3I is provided with a latching pawl (not shown) for preventing retrograde movement of the rotary dog 35. A pawl release pin 38 is rotatable in the cover 37 of the tensioning drive housing 3I and projects inwardly thereof for engagement with the holding pawl to effect retraction thereof, the outer end of the pawl release pin 38 being connected to an externally located manually operated tension release lever 39, as is best seen in FIG. 5.

The tensioning assembly 30, including the drive housing 31. the rotary dog 45 and the air motor 40. is represented in its down or Working" position in the drawings. which is the position required during actual strap tensioning. The tensioning assembly 30 swings as a unit about the axis of the pivot pin 27 and its range of swinging movement may best be observed with reference to the center line of the housing of the air motor 40. Two changed positions for the center line of this housing are illustrated in phantom in FIG. 1 and are labeled Start" and Load. Thus, at the Start position. the assembly is tilted upwardly to its maximum extent and this is a completely open position for the tool 20 which is arranged to assume this position automatically at the end of each sealing cycle to enable stripping of the tool from the sealed strap and to enable insertion of the next strap.

A latch plate 45 is mounted on the valve body casting 120 to rotate about the axis of a stud 44 with a torsion spring 46 acting to bias the latch plate 45 in a clockwise direction, as viewed in FIG. I. The latch plate 45 has an arm 47 extending inwardly of the front side plate 22 through an aperture therein and overlying and resting on a crosshead 90 of the sealer drive assembly 80, normally to maintain the latch plate in its FIG. I position. The latch plate 45 is also provided with a retaining hole 48 which is arranged to receive the tip of a retractable plunger (not shown) carried in the hub of an indexing lever 50 rotatably mounted on the bearing support 32.

The plunger is biased against the latch plate 45 and the indexing lever 50 is operable to retract the plunger. The indexing lever 50 and hence the plunger swing about the axis of the pivot pin 27 jointly with the tensioning assembly 30, and when the tool is in the Start position, the plunger is in the retaining hole 48 and maintains the parts in the Start position. At this time, a lower strap may be inserted in the tool 20.

In the position of the indexing lever 50 shown in FIG. 5, an inner angular surface 51 mates with a corresponding and oppositely facing angular surface 52 on the bearing support 32. At this time, the indexing lever 50 is to the left and permits the plunger to be shifted to the left for engagement with the retaining hole 48 in the latch plate 45. When release of the plunger from the hole 48 is required, the indexing lever 50 is elevated in a clockwise direction, as viewed in FIG. 1, the reaction of the surface 51 rotating against the surface 52 causing the lever 50 to shift to the right, as viewed in FIG. 5 to urge the plunger to the right and out of the retaining hole 48. This releases the tensioning drive housing 31 to permit it to drop into the Load position by its own weight and the force of disc springs (not shown) urging against a lifting link 56 through a separating plate 55, in a manner more fully described in the aforementioned U.S. Pat. No. 3,396,760.

When the tensioning assembly 30 is in the Load position thereof, the rotary dog 35 is still spaced somewhat above the separator plate 55 to enable insertion of the upper or supply end portion of the straps which is fed between the top of the separator plate 55 and a band type retainer spring 57. In addition, a strap guide member 58 is mounted on the outer surface of the bearing element 29 and is provided with a guide finger 59 disposed adjacent to the separator plate 55 to assist in guiding the insertion of the upper end of the straps beneath the rotary dog 35. In the preferred practice of the invention a spring loaded plunger (not shown) is provided for urging the tool toward and accurately positioning it in its Load position.

Mounted on the outer face of the rear side plate 23 is a seal feed assembly, generally designated by the numeral 60, which includes an upstanding seal storage magazine 61 and a seal feed arm 62 pivotally mounted on the rear of the seal storage magazine 61, and provided at the lower end thereof with a seal feed finger 63 extending beneath the seal storage magazine 61 for injecting a seal from the magazine into the sealing region between the side plates 22 and 23 adjacent to the base 21. The seal feed arm 62 is mounted on a pivot pin 64 and is resiliently urged by a torsion spring 65 toward rotation in a clockwise direction toward a seal feeding position, as illustrated in FIG. 1. Also mounted on the pivot pin 64 for pivotal movement with the seal feed arm 62 is a roller arm 66 which extends inwardly behind the seal storage magazine 61 for engagement with a driver lever 67 pivotally mounted as at 68 on the valve body casting 120. The drive lever 67 is coupled to the crosshead 90 for cocking the seal feed arm 62 through the roller arm 66 upon downward movement of the crosshead 90 during a sealing operation. On return of the crosshead 90 to its upper or retracted position, the seal feed arm 62 is returned to its feeding position illustrated in FIG. I by the action of the torsion spring 65, a stop arm 69 serving to limit pivotal movement of the roller arm 66 in a clockwise direction, as viewed in FIG. 1.

Fixedly secured to the front surface of the front side plate 22 is the valve body casting I20, which is integral with a circular end plate 71 ofa drive cylinder which is mounted outboard of the side plates 22 and 23. as is best seen in FIGS. 2, 5 and 7. The drive cylinder 70 is provided with a power piston 72 connected to a piston rod 73 which extends inwardly between the side plates 22 and 23, as illustrated in FIG. 2, for reciprocating movement through the cylinder 70. The valve body casting I20 is provided with an air passage 74 communicating with the interior of the cylinder 70 at the front side of the piston 72, and an air passage 74A which communicates through a fitting 75 mounted in the cy|- inder end wall '71 with one end of a flexible air conduit 76 disposed within the cylinder 70 at the front of the piston 72. The other end of the conduit 76 communicates through a fitting 77 in the piston 72 with the interior of the cylinder 70 at the rear of the piston 72. Disposed in surrounding relationship with the piston rod 73 between the end plate 71 and the piston 72 and in engagement with each, is a helical compression spring 78 which resiliently urges the piston 72 away from the end wall 7] toward the rear of the cylinder 70. for a purpose to be described more fully hereinafter. Extending outwardly from the end plate 71 at the upper and lower ends thereof are mounting ears 79 disposed in use between the front and rear side plates 22 and 23 and receiving fastening bolts therethrough to facilitate rigid mounting of the cylinder 70 in the tool 20.

A sealer drive assembly, generally designated by the numeral 80, is best illustrated in FIGS. 6 through 8. This assembly includes a power link 81 having a bifurcated end 82 pivotally engaged on a power pin 83 which is carried crosswise in the end of the piston rod 73, with a pair of rollers (not shown) being located at opposite ends of the power pin 83 to facilitate free rotation of the power link 81 within the space defined between the front and rear side plates 22 and 23. The other end of the power link 81 carries a pivot pin 85 which connects upper and lower pairs of swing links 86 and 87, respectively, in a toggle relation. The swing links 86 of the upper pair are rotatable about a fixed pivot pin 88 that extends between the side plates 22 and 23, and the swing links 87 of the lower pair are rotatable about a pivot pin 89 carried in a crosshead 90.

In FIGS. 7 and 8, the sealer drive assembly 80 is shown in its topmost or retracted position wherein the piston rod 73 is fully extended, with the piston 72 in its position illustrated in FIG. 2. In this position of the sealer drive assembly 80, the power link 8] is upwardly inclined and the swing links 86 and 87 are substantially in right angled relation. When high air pressure is applied to the front face of the piston 72 through the air passage 74, or when air pressure is removed from the rear of the piston 72 through the conduit 76 and air passage 74A. the piston rod 73 is retracted, drawing the power link 81 and the swing links 86 and 87 inwardly and driving the crosshead 90 down. As the crosshead 90 moves down, the latch plate 45 rotates clockwise, as viewed in FIG. 1. the torsion spring 46 urges the latch arm 47 in a crosshead-following mode until the retaining hole 48 registers with the plunger of the indexing lever 50. Return of the crosshead 90 to its retracted or upward position restores the latch plate 45 to its position illustrated in FIG. 1 and thereby lifts the tensioning assembly 30 to its Start position, this return movement being powered by the return stroke of the piston 72 to its FIG. 2 position, as will be described more fully below.

The lower region of the vertical chamber which is defined between the opposed vertical faces of the stationary side plates 22 and 23 receives the seal forming mechanism which is best illustrated in FIGS. 6 and 8. A pair of cam plates 9] are fixed to extend vertically along opposite sides of the lower face regions of the front side plate 22 and a corresponding pair of cum plates 92 are provided along the rear side plate 23. all to cooperate with the seal forming mechanism in a manner broadly described hereinafter. An upper set of bolts 93 are passed through the stationary side wall 23, the upper ends of the cam plates 91 and 92. the side wall 22 and the upstanding base wall 25, and are equipped with spacer sleeves 94 abutting corresponding cam plates 91 and 92 to accurately determine the assembled spaced relation of these parts. Similarly, a lower set of bolts 95 are passed through these same parts and are equipped with similar spacer sleeves 96. Each of the bolts 95 extends through an integral wing 97 provided at the lower ends of the seal storage magazine 6] (see FIGS. 1 and 7).

The sealer jaw and punch assembly as shown in FIGS. 6 and 8 includes front and rear guide plates I and l00A. the front guide plate 100 being provided with strap guide surfaces 101 that span the overlapping ends of the strap after proper insertion thereof in the tool 20, and after downward movement of the crosshead 90.

and the rear guide plate 100A being provided with a recess 101A to accommodate feeding of a seal over the overlapped portions of the strap. The distance between the strap guide surfaces 101 on the guide plate 100 is only slightly greater than the width of the strap. whereby when the guide plate I00 is lowered into strap guiding position straddling the overlapped ends of the strap it serves effectively to limit the lateral movement of the overlapped portions of the strap, thereby retaining the desired alignment of the strap while slack is being pulled out of the strap loop during tensioning of the loop about the object.

The sealer mechanism also includes pairs ofjaw pivot pins 102 and bridge holding pins 103 with the ends of the pins 102 and 103 being seated in the strap guide plates 100 and [0018. Four pairs of identical sealing jaws 105 are incorporated in the sealer mechanism with the central pairs of jaws being adjacent to each other and being separated from the outer pairs of jaws by in tervening pairs of punches 106. The punches 106 are mounted on pivot pins 104 which extend through the stacked array ofjaws and the upper ends of the jaws are connected to the lower ends of a pair of spreader links ll4 by means of link pins US, with the upper end of each spreader link 114 being pivoted to the crosshead 90 by a crosshead pin 116.

The sealer mechanism is regulated by the cam plates 91 and 92 which are fixed as previously described. The link pins 115 of the sealer are equipped at their ends with cam rollers (not shown) but ride along the surfaces of the cam plates 9| and 92 to regulate the timing of the jaw action during downward movement of the crosshead 90. Each pair of jaws 105 has a centrally located bridge I07 associated with it and each pair of punches 106 has a centrally located tie bar 108 associated with it. with the bridges 107 and tie bars 108 constituting a stacked array. The tie bars 108 function as spacers in this array and also serve to restrict the movemeat path of the punches 106. The jaws I terminate at their free ends in retention lips 109 to guide the seal when it is being fed into the sealing position between the front and rear side plates 22 and 23.

5 A stationary shear blade 0 (FIG. 6) is mounted within and alongside the lower front region of the sealer chamber between the front and rear side plates 22 and 23 which is appropriately recessed to accommodate a limited vertical floating movement for the stationary shear blade H0. A tang lll along one vertical edge of the stationary shear blade H0 nests in a corner cut out adjacent to the front side plate 22 to prevent cocking ofthe stationary shear blade. A movable shear blade 112 is nested alongside the stationary shear blade H0 and is arranged to be moved down upon downward movement of the crosshead 90 to sever the upper supply end of the strap S after folding of the seal about the overlapped portions of the strap and during deforming of the seal with the overlapped strap ends by the punches 106, with the shearing action occurring in a region of the strap which is under tension. The movable shear blade H2 is nested within the front guide plate 100 and is associated with flats provided at the front ends of the jaw pivot pins 102 to hold these pins against rotation during sealer actuation. The action of the jaws 105 and punches I06 and shear blades I and 112 in forming a joint in the overlapping strap ends and thereafter severing the supply portion of the strap is described in detail in the aforementioned US. Pat. No. 3,396,760.

Referring now also to FIGS. 9 and 10 of the drawings, the valve body casting 120 has received therein a normally closed tensioning valve 121. a normally closed guide plate lowering valve 122 and a normally open sealing valve 123, all spring-biased to their normal conditions. Compressed air is supplied in parallel to each of these valves from the external air source 43 through an input conduit 119 and an input fitting 118 (FIG. 2), and thence through an input passage 124 and a distributing passage 125 in the valve body casting 120. When the tensioning valve 12] is opened air passes therethrough to a tensioning outlet passage I26 and thence to an output fitting 126A. which is in turn connected by the conduit 42 to the input fitting 41 on the housing of the air motor 40 (FIG. 2). Air from the tensioning valve 121 also passes through a passage 127 to a cylinder 128 depending from the valve body casting 120, cylinder 128 being provided with a piston or plunger 129 disposed for engagement with the tensioning drive housing 31 for urging the tensioning assembly 30 into the Working position thereof illustrated in FIG. 1, as will be described more fully below. A ring-like end cap 129A affords clearance for the plunger [29 to move downwardly and serves as a seat for a coil spring (not shown) which reacts against the plunger 129 to automatically restore it to its retracted position after air pressure is removed from the cylinder 128.

The tensioning valve 121 is actuated by means of a tensioning trigger 130 which is generally of inverted pan shape and is pivoted to an upper region ofthe valve body casting I by means of a horizontal pivot pin 131 (FIG. 1). The tensioning trigger is provided with side flanges 132 extending downwardly therefrom at the opposite side edges thereof and front lip 133 depending from the front edge thereof. Projecting downwardly from the underside of the tensioning trigger 130 is an actuating pin 135 positioned for engaging and opening the tensioning valve I2I. An L-shaped keeper I34 is mounted on a horizontal pivot pin (not shown) located on a forward upper region of the valve body casting I20, the keeper I34 having an upwardly extending arm I36 terminating in a hook, and a horizontally extending arm terminating in a thumb release button I38. The keeper 134 is normally biased in a clockwise direction, as viewed in FIG. I, by means of a coil spring I37 which is disposed in line with the thumb release button 138 and reacts between the keeper I34 and an external shoulder on the valve body casting I20. The tensioning trigger 130 has the front lip I33 thereof shaped to define a catch oriented for engagement with the hook on the keeper arm 136.

Upon actuation and downward swinging movement of the tensioning trigger I30, the front lip I33 thereof cams past the keeper arm I36 and moves into interlocking relation therewith. The operation of the tensioning trigger I to apply air to the plunger I29 for lowering the tensioning assembly 30 to its working position in engaging the rotary dog with the strap, and to apply air to the air motor requires only momentary manual actuation, as the action of the keeper 134 maintains the tensioning trigger I30 depressed without further assist from the operator. If necessary at any time, the thumb release button I38 of the keeper 134 can be actuated to release the tensioning trigger I30 and cut off the air supply to the air motor 40 and to the plunger I29. Tension at this time would still be maintained, as the strap tension acts on the rotary dog 35 to maintain the dog penetration in the strap while the holding pawl of the rotary dog shaft 36 prevents retrograde rotation of the rotary dog 35. If desired, the ten sion release lever 39 can be operated to release the rotary dog 35 for retrograde rotation and thereby remove tension from the strap S.

Also pivotally mounted on the pivot pin I31 is a generally U-shaped guide plate lowering trigger, generally designated by the numeral I40, which extends from alongside the tensioning trigger I30 forwardly and in front of the valves 12], I22 and I23 and back alongside and adjacent to the end plate 71 of the cylinder 70. Overlying the guide plate lowering valve trigger 140 and also pivotally mounted on the pivot pin I31 is a sealing trigger I4I which is shaped similarly to the tensioning trigger I30 but is of a slightly greater width. The sealing trigger I41 is provided along the opposite side edges thereof with depending side flanges I42, and is provided along the front edge thereof with the depending front lip I43. Carried by the guide plate lowering trigger I40 adjacent to the tensioning trigger I30 and extending laterally outerly substantially parallel to the pivot pin I3I is a drive pin 144 which extends through a complementary slot in the side flange I42 of the sealing trigger I41 and beneath the lower edge of the inner side flange 132 of the tensioning trigger I30 for engagement therewith. Also integral with the guide plate lowering trigger I40 adjacent to the opposite side thereof is an actuating button 145 disposed for engagement with and actuation of the guide plate lowering I22. The sealing trigger I4] is provided on the underside thereof with a depending actuator pin I46 which is positioned for engagement with and actuation of the sealing valve 123.

Thus, when the tool 20 is at rest prior to the initiation of a tensioning and sealing cycle, air is supplied through the normally opened sealing valve I23, the air passage 74A, the fitting 75, the conduit 76 and the fitting 78 to the rear surface of the piston 72, thereby to maintain the piston 72 in its full forward position illustrated in FIG. 2, for holding the piston rod 73 fully extended against the urging of the compression spring 78 to maintain the sealer drive assembly 80 retracted. When the tensioning trigger I30 is depressed, the inner side flange 132 thereof engages the drive pin I44 and urges it and the guide plate lowering trigger I40 downwardly. thereby opening the guide plate lowering valve I22 through the action of the actuator button I45. When the guide plate lowering valve 122 is thus opened. air is admitted therethrough and through the air passage 74 to the front side of the piston 72, thereby balancing the air pressure on the opposite sides of the piston 72 and permitting it to be driven back under the urging of the compression spring 78 to a strap guiding configuration, illustrated in phantom in FIG. 2.

When the piston 72 is thus moved to its strap guiding configuration, the sealing mechanism and the guide plates I00 and 100A are partially lowered through the action of the sealer drive assembly 80 and the crosshead 90 to a strap guiding position. In this strap guiding position, the strap guide plates I00 and IO0A are lowered over the overlapped portions of the straps in straddling relationship therewith, so that the strap guide surfaces I0l are respectively disposed closely adjacent to the opposite side edges of the overlapped strap ends to restrict lateral movement thereof while accommodating longitudinal movement thereof.

When the sealing trigger 141 is depressed, the actuator pin I46 engages and closes the normally open sealing valve I23 for shutting off the supply of air therethrough to the rear surface of the piston 72 and the cylinder 70, and for connectng the air passage 74A to an exhaust port I48 in the valve body casting I20. Thus. air from the rear surface of the piston 72 is exhausted through the conduit 76 and the air passage 74A and exhaust port I48 for relieving the air pressure on the rear surface of the piston 72. Accordingly, the air pressure being maintained on the front surface of the piston 72 through the guide plate lowering valve I22 serves to drive the piston 72 to a full rearward or sealing configuration (not shown) in the cylinder for completely lowering the sealing apparatus by the action of the sealer drive assembly and crosshead to effect formation of the seal joint between the overlapping ends of the tensioned strap, in a manner described in detail in the aforementioned U.S. Pat. No. 3,396,760.

Provision is made automatically to maintain the sealing trigger I41 depressed. For this purpose, an elongated latch bar I47 is mounted for rotation about the horizontal pivot pin I31, and at one end underlies and is secured to the sealing trigger I41 to swing in unison therewith. The free end of the latch bar I47 projects across the sealer chamber and normally seats in a corner notch provided at the upper end of a cam lever (not shown) which pivotally mounted on a shank carried by the side plates 22 and 23. A torsion spring 149 encircles this shank and acts to urge the cam lever against the latch bar I47. Depression of the sealing trigger I41 elevates the free end of the latch bar 147 and allows the cam lever to rotate beneath the latch bar I47 for maintaining the sealer trigger I4I depressed throughout the power stroke of the piston 72, as is more fully explained in the aforementioned U.S. Pat. No. 3,396,760. As is also explained in that patent, as the swing links 86 and 87 complete their travel at the bottom of the sealing stroke of the crosshead 90, the upper swing links 86 strike a lug (not shown) to free the latch bar I47 and return the sealer trigger l4I to its elevated position. thus reopening the sealing valve I23 to again permit air to be transmitted to the rear surface of the piston 72.

It is an important feature of the present invention that no manual operation is required to depress the sealing valve trigger I4I, this operation being performed automatically when a predetermined tension in the strap is sensed by a tension sensing valve I50, which is of conventional construction. for example of the type sold by Chicago Pneumatic Company under Part Nos. CPSOSO Model A." The tension sensing valve 150 is mounted in a housing which is integral with the housing of the air motor 40. Referring particularly to FIGS. 3 and 4 of the drawings, the tension sensing valve I50 includes a cylindrical bushing I52 disposed in the housing 151 in surrounding relationship with a valve spindle I53 which is slidably movable longitudinally of the bushing I52. The valve spindle I53 is adapted for engagement with a valve seat or shoulder at the left-hand end of the housing I51, as viewed in FIG. 4, the other end of the spindle 153 being recessed to receive therein one end of the helical compression spring 154, the other end of which bears against an adjusting screw 155. The spring I54 normally urges the valve spindle I53 into a closed position, illustrated in FIG. 4. The sensing valve 150 is provided with an air input port 157 which communicates with the conduit 42, air passing through the sensing valve 150 and thence to the air motor 40. In operation, as the tension in the strap increases through the action of the tensioning assembly 30, the load upon the air motor 40 will, of course, increase proportionately and this load resistance is reflected by the backup pressure in the air conduit 42 leading to the air motor 40. This backup pressure is also reflected in the inlet port 157 of the sensing valve 150. When this predetermined pressure is reached. the valve spindle I53 is moved thereby to the right, as viewed in FIG. 4, against the urging of the spring 154, thereby to divert the air supply away from the air motor 40 and to an output port 158. Thus, the air motor 40 is turned off, but tension is maintained in the strap by the action of the rotary dog 35, which is held against retrograde rotation by a holding pawl. It will be appreciated that the predetermined tension at which the back-up pressure will be sufficient to shift the sensing valve 150 may be varied by adjustment of the adjusting screw 155.

The output port I58 of the sensing valve 150 is connected by a conduit 159 to an input fitting I62 ofa seal actuating assembly. generally designated by the numeral I60. As is best seen in FIG. 10, the seal actuating assembly I60 includes a body casting I6I which is fixedly secured to the rear side plate 23 by a mounting flange 164 (FIG. I), the casting I6I having formed therein a cylinder which communicates with the input fitting I62 and has received therein a piston or plunger I63 disposed immediately above the sealer valve trigger I41 for engagement therewith. When the tension sensing valve ISO is shifted by the back-up pressure in the air line 42, the air is conducted through the conduit I59 and the input fitting 162 to the cylinder of the seal actuating assembly I60, thereby serving to extend the plunger I63 for depressing the sealing trigger 141 and closing the sealing valve I23.

As the sealing trigger I41 is depressed. the front lip I43 thereof cams past the keeper arm I36 and releases the tensioning trigger 130 which is thus moved back up to its normal elevated position by the action of the spring loaded valve I2] on the actuating button I35. As the valve I2I thus recloses, the air supply to the air motor 40 and the tension sensing valve 150 and the positioning plunger I29 is shut off. Thus. the plunger I29 is retracted to permit the tensioning assembly 30 to be later returned to its Start position. and the air supply through the tension sensing valve I50 to the seal actuating assembly I60 is shut off, thereby permitting the sealing trigger I41 to he later returned to its elevated position under the urging of the spring loaded valves I22 and I23.

However, the sealing valve trigger I4] is not immediately returned to its elevated position, since it is held in the depressed position by means of the latch bar I47. as was described above, until the sealer drive assembly and the crosshead 90 reach the bottom of their power or sealing stroke. When the seal joint formation has been completed, the latch bar I47 is released and the sealing trigger I41 and the guide plate lowering trigger I40 are returned to their elevated positions, thereby reopening the sealing valve 123 and reclosing the guide plate lowering valve I22. When this occurs air is again passed through the sealing valve 123 to the rear of the piston 72, and air is exhausted from the front of the piston 72 through the air passage 74 and the exhaust port on the guide plate lowering valve 122. When this occurs the piston 72 is driven back to its retracted configuration illustrated in solid line in FIG. 2, thereby pulling the seal drive assembly and crosshead and guide plates I00 and A back to their retracted positions.

The seal actuating assembly I60 is also provided with a handle flange 168 to which is attached a top handle I65 disposed substantially at right angles to the lower handle 28 and cooperating therewith to facilitate handling and operation of the tool 20.

Referring now also to FIG. 11 of the drawings. the operation of the strapping tool 20 through an entire strapping cycle will be described. In a typical operating cycle the strapping tool 20 will be in the position indicated in FIGS. I and 2, except that the tensioning assembly 30 will be rotated upwardly so that the center line of the housing of the air motor 40 will lie along the line labeled Start in FIG. I. In this position the tensioning drive housing 3] contacts and rotates the lifting link 56 counterclockwise, as viewed in FIG. 1, to elevate the separating plate 55 above the foot section 24 of the base casting 21. The operator may now insert the lower strap end under the separator plate 55. The indexing lever 50 is then elevated clockwise as viewed in FIG. I to withdraw the plunger. as previously explained. from the retaining hole 48 in the latch plate 45, thereby allowing the tensioning assembly 30 to rotate to the Load position in FIG. I, in which position the lifting link 56 no longer acts to elevate the separator plate 55, which is therefore held against the lower strap end. In the preferred practice, the lower strap end is inserted so that the leading edge thereof extends approximately to the region underlying the seal storage magazine 61.

In this Load position, the rotary dog 35 is elevated slightly above the separator plate 55 and the operator may now feed the upper supply portion of the strap between the retainer spring 57 and the separator plate 55.

With the strap thus fed into the tool 20, the operator now depresses the tensioning trigger 130 to initiate the automatic tensioning and sealing of the strap loop. Depression of the tensioning trigger 130 serves to open the tensioning valve 121 by means of the actuating pin 135 thereby admitting air from the air source 43 through the air passages 126 and 127 to the cylinder 128 and through the air passsage I26 and conduit 42 to the tension sensing valve 150 and the air motor 40. This serves to actuate the plunger 129 forcibly to drive the tensioning assembly 30 downwardly in a counterclockwise direction, as viewed in P10. 1, to the Working position thereof to impress the rotary dog 35 into biting engagement upon the upper strap end. Simultaneously. the air motor 40 starts and drives the rotary dog 35 clockwise, as viewed in FIG. I to withdraw the supply portion of the strap and whereby tension the strap loop.

The depression of the tensioning trigger 130 also serves to depress the lowering valve trigger 140 through the action of the drive pin 144 as described above, thereby opening the strap guide lowering valve 122 through the action of the actuating button 145 and admitting air through the air passage 74 to the front side of the piston 72 in the drive cylinder 70. The air pressure on the opposite sides of the piston 72 is thus balanced, and the piston 72 is driven under the action of the compression spring 78 to its strap guiding configuration illustrated in phantom in FIG. 2, thereby moving the seal feed apparatus and the strap guide plates I and 100A to the strap guiding position thereof through the action of the sealer drive assembly 80 and crosshead 90, as was described in detail above. in this strap guiding position, the strap guide plate 100 serves to restrict lateral movement of the overlapped strap ends thereby maintaining them accurately in overlapping relationship during the tensioning operation.

The tensioning trigger 130 remains depressed throughout the tensioning operation by the action of the keeper arm 136, but tensioning can be arrested at any level by manually pressing the thumb release button 138 of the keeper 134, thereby releasing the tensioning trigger 130 and permitting the tensioning valve 121 to reclose, shutting off the air supply to the air motor 40. The holding pawl of the rotary dog shaft 36 will then retain the tension in the strap when arrested. If desired, the tension in the strap can be released by actuation of the tension release lever 39, as described above.

When the predetermined tension in the strap, as set by the adjustment of the screw 155, is reached, the tension sensing valve 150 is shifted to divert the air supply from the air motor 40 to the conduit 159 and thence to the seal actuating assembly 160. When thus disconnected from the air source, the air motor 40 stops, the predetermined tension being maintained in the strap by engagement of the rotary dog 35 therewith. With the seal actuating assembly 160 thus pressurized, the piston 163 is extended thereby engaging and depressing the sealing trigger 141 to close the sealing valve 123 through use of the actuating pin 146. The depression of the sealing trigger 141 has no effect on the guide plate lowering valve 122, since that valve is already held open by the guide plate lowering trigger I40. Closing of the normally open sealing valve 123 disconnects the air passage 74A from the air supply and connects it to the exhaust port 148 of the valve 123 for exhausting air from the rear of the piston 72. The depression of the sealing trigger 141 also serves to release the keeper arm 136 from the tensioning trigger 130, permitting the latter to be moved back up to its elevated position and permitting the tensioning valve 121 to reclose, thereby cutting off the air supply to the positioning cylinder 128 and the seal actuating assembly 160, thereby to permit the plungers 129 and 163 to be retracted. Upon retraction of the plunger 163, however, the sealing trigger 141 is held depressed by the latch bar 147, as was described above.

When the air is exhausted from the rear of the piston 72 the air pressure supplied to the front of the piston 72 through the guide plate lowering valve 122 is operative for moving the piston to its sealing configuration. thereby pulling the sealing apparatus and guide plates 100 and 100A down from the strap guiding configuration to the sealing configuration, through the action of the sealer drive assembly 80 and crosshead 90 to effect the formation of the sealed joint about the overlapped tensioned strap ends.

As the crosshead 80 lowers to its sealing position it cocks the seal feed arm 62 through the drive lever 67 as was described above. As the crosshead 80 bottoms out on its sealing stroke the shear blades I10 and 112 cooperate to sever the tensioned supply portion of the strap. When the supply portion of the strap is severed, the tension therein is released, permitting the tensioning assembly 30 to move back to its Load position. Also, when the crosshead 90 bottoms out in its sealing stroke, it permits the latch plate 45 to be rotated in a clockwise direction, as viewed in FIG. 1, under the action of the torsion spring 46 to bring the retaining hole 48 into position for receiving therein the plunger of the indexing lever 50. Also, at the bottom of its sealing stroke, the crosshead serves to release the latch bar 147 in the manner described above. thereby allowing the guide plate lowering trigger 140 and the sealing trigger 141 to return to their elevated positions, thereby permitting the guide plate lowering valve 122 to reclose and the sealing valve 123 to reopen. Thus, the air passage 74 is connected to the exhaust port of the guide plate lowering valve 122 for exhausting air from the front of the piston 72, while air pressure is again restored to the rear of the piston 72 through the air passage 74A, thereby driving piston 72 back to the front of the cylinder and pulling the sealing apparatus and the guide plates 100 and 100A back to their retracted position through the operation of the sealer drive assembly and crosshead 90, after formation of the sealed joint in the strap.

As the crosshead returns back up to its retracted position, it lifts the drive lever 67 thereby permitting the seal feed arm 62 to return to its seal feeding position under the urging of the coil spring 65, thereby driving a new seal from the seal storage magazine 61 into position between the side plates 22 and 23 for the next sealing operation. The elevation of the crosshead 90 to its retracted position also drives the latch plate arm 47 back up for rotating the latch plate 45 in a counterclockwise direction, as viewed in FIG, 1, and pulling the tensioning assembly 30 back to the Start position thereof. At this point the parts have all been restored to their original starting position, to facilitate stripping the tool 20 from the sealed strap loop and for inserting the next strap for the next strapping operation.

From the foregoing, it can be seen that there has been provided a novel pneumatically operated strapping tool for automatically tensioning and sealing a strap in response to a single manual control operation, while at the same time insuring that the overlapped portions of the strap will be maintained in proper overlapping alignment during the tensioning operation to facilitate the seal formation.

More particularly. there has been provided a strapping tool which has a strap guiding member movable from a retracted position to a strap guiding position simultaneously with the initiation of a tensioning operation for limiting lateral movement of the overlapped portions of the strap during tensioning thereof.

There is also provided a strapping tool of the character described, wherein the strap guiding member is coupled to the sealing apparatus. there also being provided novel control means for automatically moving the sealing apparatus and the strap guide member to the strap guiding position simultaneously with the initiation of the tensioning operation.

There has also been provided a strapping tool of the character described, which includes tension sensing means automatically to terminate the tensioning operation and move the sealing apparatus to a sealing condition to effect formation of the sealed joint between the overlapping portions of the strap and severance of the free end thereof when a predetermined strap tension is reached, the strapping tool automatically being returned to its original starting position on completion of the sealing operation.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means movable between a retracted position away from the strap loop and a strap guiding position alongside the opposite side edges of both of the overlapped portions of the strap for limiting lateral movement of both of the overlapped portions of the strap while freely accommodating longitudinal movement thereof, and means for moving said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means after the end portions of the strap have been placed in overlapping relationship and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.

2. The strapping tool set forth in claim 1, wherein said strap guide means includes a guide plate having a strap-receiving opening therein.

3. The strapping tool set forth in claim 1, wherein said strap guide means comprises a guide plate disposed perpendicular to the plane of the overlapped portions of the strap, said guide plate being provided 16 with a generally U-shaped notch therein having a width only slightly greater than the width of the strap for receiving the overlapped portions of the strap therein.

4. The strapping tool set forth in claim I, wherein said strap guide means includes a guide plate having a strap-receiving opening therein, said guide plate being movable between the retracted and strap guiding positions thereof in directions substantially normal to the plane of the overlapped portions of the strap.

5. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions. said strapping tool comprising tensioning means for tensioning the loop of strap about the object. sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object. strap guide means movable between a retracted position away from the strap loop and a strap guiding position alongside the opposite side edges of both of the overlapped portions of the strap for limiting lateral movement of both of the overlapped portions of the strap while freely accommodating longitudinal movement thereof, drive means coupled to said strap guide means for effecting movement thereof between the retracted and the strap guiding positions thereof, and control apparatus coupled to said drive means and actuating same to move said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means after the end portions of the strap have been placed in overlapping relationship and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.

6. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object. strap guide means movable between a retracted position away from the strap loop and a strap guiding position closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longi tudinal movement thereof, pneumatically operated drive means coupled to said strap guide means for effecting movement thereof between the retracted and the strap guiding positions thereof, and control apparatus coupled to said drive means and actuating same to move said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.

7. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object, strap guide means movable between a retracted position away from the strap loop and strap guiding position closely adjacent to the side edges of the overlapped portions of the strap for limiting movement thereof while freely accommodating longitudinal movement thereof, bias means resiliently urging said strap guide means toward the strap guiding position thereof, fluid-actuated means coupled to said sealing mechanism having a first energized condition for nor mally holding said strap guide means in the retracted position thereof against the urging of said bias means and a second energized condition for permitting said strap guide means to move to the strap guiding position thereof under the urging of said bias means, and control apparatus coupled to said fluid-actuated means for shifting thereof from the first energized condition to the second energized condition thereof at the initiation of operation of said tensioning means and for shifting of said fluid-actuated means back to the first energized condition thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.

8. The strapping tool set forth in claim 7, wherein said fluid-actuated means comprises a pneumatic cylinder having a piston coupled to said sealing mechanism.

9. The strapping tool set forth in claim 7, wherein said fluid-actuated means comprises a pneumatic cylinder having a piston coupled to said sealing mechanism, said bias means comprising a spring disposed in engagement with said piston for urging said piston toward the strap guiding position of said strap guide means.

10. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, the strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, and means for moving said sealing mechanism to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said sealing mechanism to the sealing position thereof at the termination of operation of said tensioning means and for moving said sealing mechanism back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.

11. The strapping tool set forth in claim 10, wherein said strap guide means comprises a guide plate disposed perpendicular to the plane of the overlapped portions of the strap.

12. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely ac commodating longitudinal movement thereof. drive means coupled to said sealing mechanism for effecting movement thereof among the retracted and the strap guiding and the sealing positions thereof, and control apparatus coupled to said drive means and actuating same to move said sealing mechanism to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said sealing mechanism to the sealing position thereof at the termination of operation of said tensioning means and for moving said sealing mechanism back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.

13. The strapping tool set forth in claim 12, wherein said control apparatus includes a device for automatically terminating operation of said tensioning means and initiating movement of said sealing mechanism to the sealing position thereof when a predetermined strap tension is attained.

14. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object. sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, bias means resiliently urging said sealing mechanism toward the strap guiding position thereof, fluid-actuated means coupled to said sealing mechanism having a first energized condition for norm ally holding said sealing mechanism in the retracted position thereof against the urging of said bias means and a second energized condition for permitting said sealing mechanism to move to the strap guiding position thereof under the urging of said bias means and a third energized condition for moving said sealing mechanism to the sealing position thereof, and control apparatus coupled to said fluidactuated means for shifting thereof from the first energized condition to the second energized condition thereof at the initiation of operation of said tensioning means and for shifting of said fluid-actuated means from the second energized condition to the third ener gized condition thereof at the termination of operation of said tensioning means and for shifting said sealing mechanism back to the first energized condition thereof having air pressure on one side of said piston for holding said sealing mechanism in the retracted position thereof against the urging of said bias means. said pneumatic cylinder in the second energized condition thereof having the same air pressure on both sides of said piston for permitting said sealing mechanism to he moved to the strap guiding position thereof under the urging of said bias means. and said pneumatic cylinder in the third energized condition thereof having air pressure only on the other side of said piston for driving said sealing mechanism to the sealing position thereof. it i t t 

1. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means movable between a retracted position away from the strap loop and a strap guiding position alongside the opposite side edges of both of the overlapped portions of the strap for limiting lateral movement of both of the overlapped portions of the strap while freely accommodating longitudinal movement thereof, and means for moving said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means after the end portions of the strap have been placed in overlapping relationship and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.
 2. The strapping tool set forth in claim 1, wherein said strap guide means includes a guide plate having a strap-receiving opening therein.
 3. The strapping tool set forth in claim 1, wherein said strap guide means comprises a guide plate disposed perpendicular to the plane of the overlapped portions of the strap, said guide plate being provided with a generally U-shaped notch therein having a width only slightly greater than the width of the strap for receiving the overlapped portions of the strap therein.
 4. The strapping tool set forth in claim 1, wherein said strap guide means includes a guide plate having a strap-receiving opening therein, said guide plate being movable between the retracted and strap guiding positions thereof in directions substantially normal to the plane of the overlapped portions of the strap.
 5. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object, strap guide means movable between a retracted position away from the strap loop and a strap guiding position alongside the opposite side edges of both of the overlapped portions of the strap for limiting lateral movement of both of the overlapped portions of the strap while freely accommodating longitudinal movement thereof, drive means coupled to said strap guide means for effecting movement thereof between the retracted and the strap guiding positions thereof, and control apparatus coupled to said drive means and actuating same to move said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means after the end porTions of the strap have been placed in overlapping relationship and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.
 6. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object, strap guide means movable between a retracted position away from the strap loop and a strap guiding position closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, pneumatically operated drive means coupled to said strap guide means for effecting movement thereof between the retracted and the strap guiding positions thereof, and control apparatus coupled to said drive means and actuating same to move said strap guide means to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said strap guide means back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.
 7. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism for sealing together the overlapped portions of the tensioned strap to secure the strap about the object, strap guide means movable between a retracted position away from the strap loop and strap guiding position closely adjacent to the side edges of the overlapped portions of the strap for limiting movement thereof while freely accommodating longitudinal movement thereof, bias means resiliently urging said strap guide means toward the strap guiding position thereof, fluid-actuated means coupled to said sealing mechanism having a first energized condition for normally holding said strap guide means in the retracted position thereof against the urging of said bias means and a second energized condition for permitting said strap guide means to move to the strap guiding position thereof under the urging of said bias means, and control apparatus coupled to said fluid-actuated means for shifting thereof from the first energized condition to the second energized condition thereof at the initiation of operation of said tensioning means and for shifting of said fluid-actuated means back to the first energized condition thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate sealing thereof.
 8. The strapping tool set forth in claim 7, wherein said fluid-actuated means comprises a pneumatic cylinder having a piston coupled to said sealing mechanism.
 9. The strapping tool set forth in claim 7, wherein said fluid-actuated means comprises a pneumatic cylinder having a piston coupled to said sealing mechanism, said bias means comprising a spring disposed in engagement with said piston for urging said piston toward the strap guiding position of said strap guide means.
 10. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overLapped portions of the tensioned strap to secure the strap about the associated object, the strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, and means for moving said sealing mechanism to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said sealing mechanism to the sealing position thereof at the termination of operation of said tensioning means and for moving said sealing mechanism back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.
 11. The strapping tool set forth in claim 10, wherein said strap guide means comprises a guide plate disposed perpendicular to the plane of the overlapped portions of the strap.
 12. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, drive means coupled to said sealing mechanism for effecting movement thereof among the retracted and the strap guiding and the sealing positions thereof, and control apparatus coupled to said drive means and actuating same to move said sealing mechanism to the strap guiding position thereof at the initiation of operation of said tensioning means and for moving said sealing mechanism to the sealing position thereof at the termination of operation of said tensioning means and for moving said sealing mechanism back to the retracted position thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.
 13. The strapping tool set forth in claim 12, wherein said control apparatus includes a device for automatically terminating operation of said tensioning means and initiating movement of said sealing mechanism to the sealing position thereof when a predetermined strap tension is attained.
 14. A strapping tool for applying a length of strap around an object in a loop with overlapping end portions, said strapping tool comprising tensioning means for tensioning the loop of strap about the object, sealing mechanism movable among a retracted position and a strap guiding position and a sealing position for sealing together the overlapped portions of the tensioned strap to secure the strap about the associated object, strap guide means coupled to said sealing mechanism for movement therewith among the retracted and the strap guiding and the sealing positions thereof, said strap guide means in the strap guiding position of said sealing mechanism being disposed closely adjacent to the side edges of the overlapped portions of the strap for limiting lateral movement thereof while freely accommodating longitudinal movement thereof, bias means resiliently urging saiD sealing mechanism toward the strap guiding position thereof, fluid-actuated means coupled to said sealing mechanism having a first energized condition for normally holding said sealing mechanism in the retracted position thereof against the urging of said bias means and a second energized condition for permitting said sealing mechanism to move to the strap guiding position thereof under the urging of said bias means and a third energized condition for moving said sealing mechanism to the sealing position thereof, and control apparatus coupled to said fluid-actuated means for shifting thereof from the first energized condition to the second energized condition thereof at the initiation of operation of said tensioning means and for shifting of said fluid-actuated means from the second energized condition to the third energized condition thereof at the termination of operation of said tensioning means and for shifting said sealing mechanism back to the first energized condition thereof after sealing of the tensioned strap, whereby said strap guide means insures that the end portions of the strap loop will remain in overlapping relationship during tensioning of the loop to facilitate the sealing thereof.
 15. The strapping tool set forth in claim 14, wherein said fluid-actuated means comprises a pneumatic cylinder having a piston coupled to said sealing mechanism, said bias means comprising a spring disposed in engagement with said piston for urging said piston toward the strap guiding position of said strap guide means, said pneumatic cylinder in the first energized condition thereof having air pressure on one side of said piston for holding said sealing mechanism in the retracted position thereof against the urging of said bias means, said pneumatic cylinder in the second energized condition thereof having the same air pressure on both sides of said piston for permitting said sealing mechanism to be moved to the strap guiding position thereof under the urging of said bias means, and said pneumatic cylinder in the third energized condition thereof having air pressure only on the other side of said piston for driving said sealing mechanism to the sealing position thereof. 